Label-independent detection (LID) optical readers can be used, for example, to detect drug binding to a target molecule such as a protein, or changes in living cells as material within a cell is displaced in response to a drug. Certain types of LID optical readers measure changes in the refractive index on the surface of a resonant waveguide grating (RWG) biosensor for an array of RWG biosensors. The individual RWG biosensors are located in respective wells of a microplate.
In one type of LID optical reader, narrowband light is swept over a range of wavelengths and directed to each RWG biosensor using a narrow-band tunable light source. To ensure accurate RWG biosensor measurement, the center wavelength of the narrowband light must be known to a high degree of resolution with respect to the particular wavelength tuning parameter used to tune the center wavelength. To date, achieving such high resolution has proven to be very expensive. Alternative systems and methods are needed for cost-effective wavelength tuning that can be referenced to a reference wavelength while also meeting high-resolution requirements with respect to the wavelength tuning parameter.